Harry Potter and the Demons at Hogwarts
by Itzika
Summary: BIG crossover. Brief explanation of each plot given in the story! Their worlds aren’t as fun to watch when they’re separate, so someone decides to mix them up. Watch as lives are rewritten and the laws of physics become mere suggestions. ON HIATUS
1. Prologue

Disclaimer: _(said in one breath)_ I do not own Harry Potter, Yu Yu Hakusho, Yu-Gi-Oh!, Sailor Moon, Cardcaptor Sakura, or Naruto, but I do own Checkmate and her crazy, mixed-up, mashed-up, physics-laws-breaking powers.

Summary: YYH/YGO/CS/SM/Naruto/HP crossover (Brief explanation of each plot given in the story!) Their worlds aren't as fun to watch when they're separate, so someone decides to mix them up. Watch as lives are rewritten and the laws of physics become mere suggestions.

You can skip most of this if you know all the stories. I've starred what is from me, so DON'T MISS THAT! It is CRUCIAL to the story! And you find out who'll be there in the last sentence of every paragraph. You don't want to be overwhelmed by the number of characters or be waiting for people who aren't coming, now do you? And you HAVE to know what's happening here.

Prologue: Checkmate

There was a porcelain doll sitting on the girl's lap, which she continually stroked as she observed the floating chessboards. Each held an array of a multitude of colorful characters that properly belonged in a role-playing game, not on such a traditional board. The tiny girl lifted her hand and touched one of the pieces. The figure had wildly long black hair and markings all over its muscular body. The girl began petting it, empty eyes fixed on the board.

"Urameshi Yusuke," she said softly. "Reikai Tantei, Spirit Detective. His gift is with the Reigun, the Spirit Gun, a burst of spirit energy which decimates most enemies. His teammates are Kuwabara Kazuma, a powerfully aware human;" her hand moved to a figure with an orange sword in hand and even more vividly orange hair, "Kurama, a kitsune;" she touched a red-haired figure holding a rose; "Jaganshi Hiei, son of a Koorime;" she touched the small black-hared figure. "He knows many psychics, and he knows the famous psychic Genkai," and she touched the smallest figure, a pink-haired, brown-eyed woman. "His… boss… is Koenma, prince of the underworld," and she touched a toddler that was only taller than Genkai by virtue of his impressively large hat. "We choose… the Tantei team, Genkai, the demons Jin, Touya, and Rinku; and the psychics Gamemaster, Doctor, Mitarai Kiyoshi, Hagiri Kaname, Kido Asato, Kaitou Yuu, and Yanagisawa Mitsunari… to participate in the coming game."

She moved her attention to another chessboard, apparently not noticing as the chosen figures vanished from the board to a new one which had not previously been there.

"Motou Yugi," she whispered. "Possesses the Millennium Puzzle, which when assembled appears to be an upside-down pyramid and contains the soul of an ancient Egyptian pharaoh. The other items of interest are the Ring, which belongs to Ryou Bakura and the inhabiting spirit Bakura, King of Thieves; and the Rod, which after belonging to Ishtar Malik and splitting him, creating Marik, has found its way to Kaiba Seto, president of a multibillion dollar gaming industry. We choose these four… seven… to participate in the coming game."

Another chessboard was selected.

"The ninja Uzumaki Naruto." Her voice this time was slow. "Carries a demon fox within him. While it is bound by a powerful sealing spell, Naruto has begun harnessing its energy, sometimes unintentionally. His teammates are Uchiha Sasuke," referring to a dark-haired boy, "and Haruno Sakura," a pink-haired girl. "Their teacher is Hatake Kakashi," who was a gray-haired man with his headband over one eye and a covering over his mouth. "Other shinobi are the sand ninja Gaara, Temari, and Kankurou; the second-year leaf ninja Neji, Tenten, and Lee; the other newbies from hidden-in-the-leaves: Hinata, Kiba, Shino, Ino, Shikamaru, and Choji; and the sound ninja Dosu, Kin, and Zaku." The doll's face caught the light as the girl's eyes glittered. "We choose all of them to participate in the coming games."

Now only three boards were left. The girl touched the blond ponytails of a figure on the middle board. "Tsukino Serena," she said. "Sailor Moon. She is responsible for saving the world many times, along with Anderson Amy, Hino Raye, Lita, and Mina." She touched each of the Sailor Senshi in turn. "They hail from the first five planets of the solar system, all but Sailor Moon. She, their princess, is of the moon as her name suggests. Her prince, Darien, is from Earth." She touched a dark-haired boy's figure. "Darien and Serena are destined to fall in love and have Rini, the princess of Crystal Tokyo." Rini was a tiny figure with pink ponytails. The girl leaned forward. "We choose all of them to participate in the coming games."

The next board had relatively few characters. The girl touched each one before settling on a small girl with short brown hair and an eternally happy smile. "Kinomoto Sakura," she said with more breath than voice. "The most powerful magician in her world. Master of the former Clow Cards, now Sakura Cards, and of their two guardians, Yue—" who was a tall, silver-haired figure with wings "—whose temporary form is Yukito, and Cerberus," who turned out to be a golden lion with a metal adornment instead of a mane and with wings identical to Yue's, large, feathery and angelic, "whose temporary form resembles a stuffed animal. Her brother is Kinomoto Toya." Toya had darker hair than Sakura's and was much older. "She loves, and is loved by, Li Syaoran." Syaoran was a boy with a rebellious expression and brown hair. "He is a descendant of Clow Reed, who created the Clow Cards and was reincarnated as Eriol," a black-haired, gentle boy about Sakura's age, "and as Sakura's father. Eriol's new servants are Ruby Moon," an (apparently) female red-haired beauty with butterfly wings, "who disguises herself as Akizuki Nakuru, and Spinel Sun," who was a black panther with similar wings, "who resembles, when he so desires, a black cat with wings. Eriol loves, and is loved by, Mizuki Kaho," who was a tall, beautiful woman with brown hair and an oddly shaped bell. She put a finger to her lips in thought. "We choose… Sakura, Syaoran, Eriol, Mizuki Kaho, Yue, Cerberus, Toya, Ruby Moon, and Spinel Sun."

There was now only one board. The girl placed her hands on either side of the board and stared down at it hungrily. "Harry Potter," she said to a black-haired, green-eyed, bespectacled boy. "The Boy Who Lived." Her eyes roamed around the board. She smiled. "The battle will take place on a world like theirs. Theirs is the blueprint for the field of this game."

As the board fused with the one above it, the one on which the selected figurines now stood, the girl closed her eyes, took the doll's hands in her own, and spoke.

"Only that knowledge which is needed shall remain,

With no source for this knowledge these player's memories to stain.

Trapped within a different world, one not all their own,

Only to find the seeds of malice have already there been sown."

She looked down and chanted, more quickly.

"Let the wards now be broken

That the games may begin.

Let the doors all be opened

And the players welcomed in."

At once the board began to spin. When it stopped, the players were arranged in neat ranks along the sides of the board. Shadowy figures stood along the other side of the board.

The girl smiled and lifted the figure of the red-haired, blue-eyed, horned demon and the one with silver-and-green hair and set them down along the ranks. Her eyes glittered, a sight somehow not as frightening as the emptiness they had held in the beginning.

"Demons to E-7."

Well. That's the beginning of my super-creepy, super-weird fanfic. What do you think? Please review, even if you're just going to flame me. I don't want to waste my time on something no one likes. (Although I promise, you don't know half the story and it will involve the characters mentioned… in small groups, though, so you can keep track of them.)


	2. Chapter 1

Disclaimer: I do not own _(straightens glasses, looks at paper)_ Yu Yu Hakusho, Yu-Gi-Oh, Naruto, Sailor Moon, Cardcaptor Sakura, or Harry Potter. I do own Checkmate, and I own her creepy little non-dimension and her creepy boards and her mixed-up-mashed-up-physics-laws-breaking powers. (I just needed someone to be a gamemaster, and she's fun… when she doesn't make me hate her. So please don't hate me for having only my OC last chapter!)

Thanks for sticking with me! Okay, just so you know: the first year is mine, too. It's one year before the Harry Potter series actually started. Also, their memories had to be shifted around a bit; that's what the first chant did. Things happened earlier than they should've, and some things didn't actually happen, but the changes that followed _did_. Very confusing… You'll see some of the changes in this chapter. Now, on with it!

Chapter One: Demons to E-7

Touya stared out to window at the tops of the buildings below. The window of the apartment had almost completely frosted over, which was no real surprise since Touya's body temperature was barely above freezing.

Jin walked in from the other room. "Hey, Touya," he asked, "wanna go grab a drink?"

Touya didn't even blink. "No."

Jin walked up, bent down, and looked hard at Touya's empty, ice blue eyes. His expression softened. "Touya, you can' keep beatin' yerself up over tha'," he told his fellow shinobi. "It wasn't your fault." Touya didn't respond; Jin sighed. Not a year before, the other three shinobi—Gama, Bakken, and Risho—had gone on individual missions, and had never come back. Touya had never forgiven himself. Unlike Jin, who had been on a mission of his own, he had been trapped at their dojo, waiting for his sickness to pass. Jin hesitated, then finally said what he was thinking. "Look, Touya, it's not like ya coulda dun anythin' even if you 'ad been there. It was _hot_. Even Ah was abou' to pass out, Ah though'."

Touya's fist slammed the wall in frustration. "I _hate _that!" he shouted, angered out of his usual calm. "Why me? Why then? I had to be sick when they died. If I hadn't been so _weak_, I could've done something!"

Jin stood and looked down at his friend sadly. Every five years, Touya's kind suffered a severe illness, when their body temperature rose to what is cold to most, but dangerously high for an ice demon. Touya had been locked in a room that nearly froze anyone and anything that came too near in an attempt to lower his temperature. Jin tried again.

"Look, man, ye're the ice master. Even without the illness, it would'a been too 'ot for ya."

Touya's shoulders slackened. He straightened and breathed deeply for a few moments. When he opened his eyes again, he was back to being calm, methodical Touya. "Every time," he whispered. "It's always defined by _what_ we are, not _who _we are… wouldn't you say, Jin?"

Jin was staring out the window. He opened and closed his mouth several times before finally managing to speak. "Uh… Touya… I'm not so sure this is the best time to talk about something so serious… I'm not even sure this isn't a dream."

Touya followed Jin's gaze and saw the owl hovering outside the window, a letter tied to its leg.. He stood and quickly opened the window.

Jin blinked. "You sure that's the best idea, Touya? What if it's… I dunno… somethin' dangerous?"

Touya pulled the letter off the owl's leg. "Better to deal with it than draw attention to ourselves," he reasoned aloud. "That was one of the conditions for coming to live here, remember?"

"'Don't break any of Reikai, Makai, or Ningenkai's laws; don't traffic anything with inhuman energy; don't draw attention to the fact that we're not human.'" Jin recited. "'Ow's that bird gonna mess it up for us?"

Touya read the letter, looking more and more stunned with every word. "Owls are nocturnal," he said as though in a daze, handing the letter to Jin. "They don't come out during the day—except, apparently, to bring impossible messages."

Jin took it. The letter read:

_Dear Mr. Jin and Mr. Touya of the Shinobi,_

_We are pleased to inform you that you have been accepted into Hogwarts School of Witchcraft and Wizardry. Term begins on September 1. Please find enclosed a list of your required books and equipment._

_Please understand that this is an English school. If you accept our invitation, a representative of the school will be sent to your place of residence at 3:00 P.M. on August 17. If necessary, you will be given language charms during the seven-year course._

_Please send the owl back with your answer._

Minerva McGonagall

Deputy Headmistress 

_P.S. Do you have a fireplace?_

"Do we 'ave a _fireplace?" _Jin repeated incredulously. "Uh… 'Ow d'you say 'Yah, but we don' use it, since mah buddy's an ice demon 'oo'll burn up if 'is temp' gets too far above 45' in English?"

"Jin…" Touya said. "I don't think they know we're demons."

Jin looked up then back down at the paper. "Hey, ya migh' be right," he said, surprised. "It stinks o' human. 'Ey, dus'at mean we can' do it?"

"You're not serious."

"Wha'? It's better than sittin' 'round mopin'."

Touya looked more closely at the paper, then back to his reflection in the window. When he compressed his energy, made himself seem as young as he could, he could barely pass for twelve as a human; Jin could go a little younger. They could, if they wanted to…

"We'd have to ask Reikai, though," Touya mused.

"_Ask _'em? Heck no! We'll _tell _'em! These guys invited us, an' all we gotta do is accept."

Touya looked at his overexcited fellow shinobi. Jin was serious about this. That was all he needed to know. Jin would go one way or the other, and he knew Touya would follow to keep him from doing anything stupid.

He sighed and wrote on a piece of scrap paper, _Yes._ He gave this to the owl, which flew out the window.

Another owl, if the demons had strained their eyes, could have been seen flying across the horizon, with a letter addressed _To the Spirit-seer and the Guardians._

Thanks to all who bore with me! I realize this is weird… but don't worry! Only a few from each world will be entering the fray this year! If you must flame me, I will cry… but then I might give up, which I'm sure would be your goal. Next up: the world of Cardcaptor Sakura awaits! Let's see how a five-year-old can be the most powerful magician in the world!


	3. Chapter 2

Disclaimer: I own Checkmate. I own the changes she makes (the sickness that hits ice demons, the new subjects that will be taught). I don't own Yu Yu Hakusho, Yu-Gi-Oh, Naruto, Sailor Moon, Cardcaptor Sakura, or Harry Potter. Now, on with it!

Chapter Two: To the Spirit-seer and the Guardians

"You're NOT going?"

Toya was stunned. Yukito and Nakuru had been offered the same chance he had, with one tiny little exception: _They were turning it down!_ Toya couldn't even imagine going so far away and leaving his boyfriend behind.

Yukito truly looked sorry. "I'm sorry, Toya," he said again, "but, well… you know… I can't be so far away from Sakura for very long."

"You mean _Yue _can't be so far away from Sakura for very long."

The girl in question was standing just outside the room. Toya hadn't noticed his little sister's presence, and Yukito didn't have any awareness whatsoever; but Yue knew, and why he kept the secret was a mystery. Under normal circumstances he would have told Yukito the moment Yue's master appeared. But this time, Sakura sank to the floor and curled into a tight ball without either of them noticing.

It had all been a dream, of a kind. Sakura had become the Master of the Clow and had changed the cards to become the most powerful magician in the world… but her body had been left behind, floating in a coma through the ages of three and four. Eriol had apologized many times, but it did become annoying when she was more advanced than any five-year-olds around, and people wouldn't let her take middle school like she'd been in when she was in that alternate reality. True, she had been getting B's and C's in middle school, but now she was stuck in third grade. Advanced as it was for a five-year-old, Sakura had already learned everything from third grade. The biggest change she'd dealt with, coming back to reality, was Toya. He and Yukito were dating, and he still had his magic. Sakura's position as Master of the cards hadn't fazed him one bit. Now he was invited to a magic school, and Sakura didn't want him to be mad at her for Yukito being stuck behind.

"Toya," Yukito was saying, "Yue… I'm his temporary form. There's no way to separate us from each other."

Sakura was crying now, crying for Toya and for Yukito, the boy she owed so much, and took so much from. It was one of her quiet sobs that finally alerted Toya and Yukito to her presence.

"Who—Hey!" Toya was angry, not play-angry like when she stomped on his foot, but real-angry. "Squirt, what're you doing listening in?"

"Sounds like you just answered your own question, Toya." Nakuru pushed past Toya and brushed Sakura's hair back. "Hey, Sakura. It's no big deal. What did you hear?"

Sakura wiped her eyes. Yukito was having an internal conversation with Yue, she could tell that much, but what they were saying was an unknown. If she wanted to, Eriol said she could probe; but he'd been proud of her when she'd answered that Yukito and Yue could say what they wanted to each other and she wouldn't listen.

When she opened her eyes, Toya had gone back to the paper and was writing his response. Nakuru poked her head over Toya's shoulder and read it aloud. "Dear Professor McGonagall, I accept your invitation to Hogwarts school, but Yukito and Nakuru will be unable to attend until Sakura and Eriol can come as well. Sincerely, Kinomoto Toya."

Professor McGonagall handed the paper to Dumbledore. "Which makes three who accept the invitation, two who don't," he said. "What of the sound ninja?"

Professor McGonagall looked at the paper. "Otogakure is far from here, Albus. It will take some time for the letter to be delivered in each direction." She looked back at Albus. "You do realize that they're the servants of a snake."


	4. Chapter 3

Disclaimer: Raise your hand if you don't already know what parts of this I do and do not own. If you just raised your hand, skip back to the prologue and start from there.

Chapter Three: Servants of a Snake

Dosu was thrown back by the blast of sound and air from Zaku's hands. He slowly pulled himself up to his feet. "Neat trick, Zaku," he admitted grudgingly. "But now it's my turn." He pulled back the sleeve covering his right arm and focused his chakra in the amplifier strapped to it. The amplifier switch flicked to 11.

Kin watched from the sidelines, dark eyes drinking in every detail of the fight. Their master, the giant snake Orochimaru, slipped up beside her. "Enjoying the show?" he asked Kin, the only female among his eleven-year-old charges.

Kin gasped. Clearly, she hadn't heard his approach. She calmed herself and changed the subject. "Lord Orochimaru, I believe Dosu informed you of the letters we each received?"

"Yes… he did at that. Why the interest, Kin-chan?"

Kin almost flinched. He sounded like a predator when he called her Kin-chan, like the men her mother had slept with, a new partner every night until Kin had killed her. Seven needles, all hitting the jugular vein within half a centimeter of each other. It had been that night that she'd caught Orochimaru's attention. "Well…" Kin had almost lost the thread of her conversation. "I—I thought… it might be interesting. We might learn something new, something the people of the other villages don't know how to combat."

Orochimaru laughed. "Kin-chan, if you want to go, just ask." His eyes caught hers. "Truth be told, I was considering sending you three. At the very least, it promises to be entertaining."

Kin looked up at her master. "Then… Lord Orochimaru, I… can we? I think it would be…"

Orochimaru caught her chin. "Of course, Kin," he answered smoothly. "You can go. You can all go." He bent down and kissed her cheek.

Kin grew pale and stumbled back. "I have to… go…" she managed to get out before she turned and ran.

She hated him! _Hated_ Orochimaru! He never should have saved her! He never should have decided to train her… Those boys. Kin skidded to a halt. _Boys._ Boys would be coming to this place called Hogwarts. The other two boys Orochimaru fostered would be there; it stood to reason they wouldn't be the only ones.

Zaku noticed when she left, but ignored her. Kin was always on edge around Lord Orochimaru, especially when he touched her or—gag—_kissed_ her. Zaku didn't know what Orochimaru wanted to do that for, but he did strange things to Dosu and Zaku as well. Zaku, who had slaughtered half a neighboring village, had repeatedly turned to find that Orochimaru had left something belonging to a dead villager. More than once Zaku had fought away the urge to be sick, and more than once he'd failed.

Dosu, on the other hand, had had an almost opposite experience to Zaku's. He'd been beaten by his father repeatedly from the time he was three until he was seven, at which point he'd screamed, unconsciously amplifying the scream with chakra, and broken his father's eardrums. He'd then taken a knife and stabbed his father to death. Later, he'd claimed he couldn't remember it, but Orochimaru would only ever let him fight with that one kind of curved knife. Dosu hated him for it.

Orochimaru knew the children despised him, and loved it. It was only a matter of time, as their hatred for him forced their strength to grow ever greater, so that they could destroy him.

There was only one more owl to pass the one with the sound ninja's letters. This one carried a message to the husband of the princess of the moon kingdom.

_(Cowers and covers head)_ Aah! Don't hate me for making Orochimaru a pervert! Or for giving the Otonin back-stories! I didn't mean to! (No seriously, it just happened.) Please review! I've already written the next chapter, so even if you flame me I'll probably update, but I can fix it! (Unless you just don't like crossovers, then too bad for you.)


	5. Chapter 4

Disclaimer: If you have to read this, you shouldn't be this far.

Chapter Four: The Husband of the Princess of the Moon Kingdom

Darien looked at his hands, rather than face the red-haired man who had come to deliver his invitation to Hogwarts. "I…" he whispered. "I'm sorry, I… I just don't know anymore. I mean…" He closed his eyes tightly. What _did _he mean? "I mean, I…Serena's here, and she's the only one… the only one I remember."

Bill patted the boy's shoulder awkwardly. Damn, why did little kids always have to seem so fragile? Bill hated feeling like anything he said was going to break them. "Hey, c'mon," he said in what he hoped was an encouraging tone. "What happened to that happy, confident response?"

Darien smiled. "Serena was here when I wrote it," he admitted. "She kept telling me it was okay, it was good."

Bill pulled Darien up off the bed into a standing position. "And she was right," he told Darien. "It's okay, it's good… c'mon, let's go."

Darien sniffed and took Bill's hand. "I need to tell the doctors," he mumbled, following Bill into the hall. "You hafta sign some stuff."

Bill waved a hand in a broad gesture that made a passing nurse duck. "Already taken care of, little guy," he said dismissively. In truth, no one had the heart to tell Darien that despite his high IQ test results, the fact remained that he was a boy, no longer an infant, and he had amnesia. The doctors were more than happy to give Bill temporary foster care, in reality only temporary until he could modify their memories and get the kid registered as a wizard in their underground society. But the kid didn't need to know that. "Let's go."

Darien nodded and followed Bill to an empty hallway. Bill took out a small brochure and instructed Darien to touch it. Five seconds later, they were off, on their way to Diagon Alley.

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Okay, I will update faster if I get reviews! But you knew that. So review! _(Throws mini-tantrum)_ Review review review review review!


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